Four novels into a relationship with Jim Crace - I was a late starter with 1997's Quarantine -one begins to see how the trick is done. At a time when one significant strand of the English novel is busy reinventing itself around the ideas of settlement and rootedness, Crace's books are set, well, nowhere in particular. Quarantine trailed Our Lord around his 40-day sojourn in a necessarily anonymous wilderness. Being Dead (1999), the one about the pair of murdered corpses decaying in the sand dunes, might just have taken place in Australia. And now comes Six, located in some proud East European capital liable to flooding that a faint geographical hunch leads me to presume is Budapest.

In some ways this habitual topographical vagueness is highly appropriate for the elemental themes on display. Crace's novels are sharply, even bitterly determinist, full of the most primitive stirrings and motivations, with base humanity always ripe to be left behind in the biological slipstream. The food/sex tie-up is much in evidence, while feeling takes place as much in the groin as in the head: Felix Dern, the protagonist of Six, must be due some kind of award for the number of erections he manages to sustain in the scant 180 pages at his disposal.

Feminine heat, too, is always stoking up the wider temperature: "Her skin was turning red. Blood was pumping to the surface of her face and chest. Blood congested in her lips and nose, her earlobes and her nipples..." Yet however stoutly lashed to the engines of human desire and striving, the prevailing urge is always bleakly naturalistic. Discovering herself pregnant by Felix, his second wife Mouetta decides that "His purpose has been served... Biology has overtaken him." Let us not forget, Crace reminds us in one of his frequent authorial admonitions, "that Lix, indeed, was just an animal, compelled by base impulses to spend his seed..." Sensuality and the deft psychological glance have their place, the argument runs, but in the end it all comes back to Darwin.

Crace's characters rarely evoke much fellow-feeling in the reader - the two in Being Dead were notably charmless - but it is possible to feel a certain amount of sympathy for Felix. A celebrated actor in his late 40s, with a strawberry birthmark, and more timorous than his celebrity would make onlookers assume, Felix's signature mark is his fertility. Every woman he sleeps with will eventually end up impregnated. Six, whose title refers to the number of our man's progeny, opens with the latest of these significant couplings, when Felix and Mouetta are forced, by civil disturbance, to spend the night in their car, going on to eat an edgy hormonal breakfast in a fashionable café. Again the biological tocsin clangs away: "Mouetta was the woman he required. This is the nature of the beast."

A trawl back in time then ranges over her predecessors: the older woman in student days; Mouetta's activist cousin Freda; plump, well-connected Alicia; an actress with whom he consummates his passion on the stage of a deserted theatre. Lurking all the while in the wings are the pre- and post-glasnost history of Budapest, or wherever it is, with its thaws, freeze-ups and liberation problems, and the tantalising, though always shadowy, figures of Felix's children.

Technically, Six is an odd mixture of obliquity and heavy emphasis. While the urban backdrops, with their hints of danger and unrest, are sketched in with the lightest of touches, much of the foregrounded psychology, though highly acute, looks over-explained.

The scene in which Felix and Mouetta eat their post-conception breakfast is a case in point: so adept is Crace at showing how Lix misreads his wife's emotional semaphore that the reader is uneasily conscious of having too little to do. Exploding in the background, meanwhile, is a salvo of heavy-duty aphorisms ("A woman is renewed by clothes", "Chatter is the cheapest contraceptive") that close inspection reveals to have rather less to them than meets the eye. Stylishly done, and full of well-concealed trickery, Six is like everything Crace has written: a glossy and elegant conceit but, in the end, not much more than that.